Thank you all for your replies!

Wyld: Oh, I always wanted to, always would have taken the next step, it's just that I never had the right person or right opportunity to do so before.

Kahlann: I know, I try! Sometimes it all goes really well and I don't have any such problems... and sometimes we manage to smooth them over... but there's just those times when I keep worrying! 'Oh dear, I feel half-like-peeing, but he's just tying my hands in front of me and bending me over for a spanking... if that's all I can just go pee later... but what if he's actually planning for a long session? (he likes the element of surprise, and I do too, it'd quite spoil the experience to be told what will happen to me in advance) In that case I'd better go now, before it gets more intricate...'

Just to clarify, he doesn't really mind untying me to go pee, tying my hair up for me, etc, it's just that it's a minor annoyance to us both to need to keep interrupting the scene... and I don't like that. I want to try and relax and not think so much about such things and just enjoy the bondage... but what if I don't realize that I need to pee or that I haven't eaten for the past 6 hours and am close to gastritis, and it just occurs to me when he's gotten me into intricate shibari that took 20 minutes to prepare?

We're both very new to this, first time for both of us even though we've both read/watched lots of stuff, and I've tried quite a bit of self-bondage before.

Edit: fetishdj, good idea... I suppose I'll try suggesting it to him, or maybe he'll come around to thinking of that as well, if it begins to bother him.